Professional porting

You guys are quite polite. It never ceases to amaze me. I might be kinda weird.

wireman wrote:

well ive got some pictures somewhere of a gpz/j head i did but cant find them:S so ill just type out one of my usual longass posts for ya! anyway use your new intake boots for guide to scribe outside of ports then gradually funnel ports getting gradually smaller as you go in towards bowl area.do not polish intake ports,leave them a little rough to keep air/fuel mixed up and do not go crazy removing material from intake ports this will only kill low-midrange power which is what you really need for a streetbike.on the exhuast side i like to make bottem of port kinda flat and concentrate on top of port since that is the natural area exhuast will concentrate when leaving combustion chamber.you will end up with something resembling a D laying on its back,use an old exhuast crush gasket as a guide to scribe around port keep the D shape slightly smaller then your scribed line to prevent reversion back into port from header.just clean up bowl area,dont try reshaping things.stocksize valves are fine for smaller motor no need for all that fancy stainless stuff,just good springs and shim under buckets to go with those big cams!:evil: if you can swing it id reccomend having combustion chambers,valve faces ,piston domes and chambers done in piston coat.oh yeah dont forget to clearance head for cams and a good valve job.

Exitpupil

The above is the most accurate description on this thread as to how to do your head.

Good luck

Jay

Thanks. It's nice to have what I thought reinforced.

Porting also has to include some consideration of velocity.Seen lots of heads that had huge cfm #'s but wouldn't help a motor get out of its own way because the port velocity was ignored.

Go with APE Jay's recommendation, as stated he didn't get where he is by screwing up...1075 with 410's is a killer combo.Throw in some 29 smoothbores and surprise a few current sportbike owners. I have.

APE Jay wrote:

wireman wrote:

well ive got some pictures somewhere of a gpz/j head i did but cant find them:S so ill just type out one of my usual longass posts for ya! anyway use your new intake boots for guide to scribe outside of ports then gradually funnel ports getting gradually smaller as you go in towards bowl area.do not polish intake ports,leave them a little rough to keep air/fuel mixed up and do not go crazy removing material from intake ports this will only kill low-midrange power which is what you really need for a streetbike.on the exhuast side i like to make bottem of port kinda flat and concentrate on top of port since that is the natural area exhuast will concentrate when leaving combustion chamber.you will end up with something resembling a D laying on its back,use an old exhuast crush gasket as a guide to scribe around port keep the D shape slightly smaller then your scribed line to prevent reversion back into port from header.just clean up bowl area,dont try reshaping things.stocksize valves are fine for smaller motor no need for all that fancy stainless stuff,just good springs and shim under buckets to go with those big cams!:evil: if you can swing it id reccomend having combustion chambers,valve faces ,piston domes and chambers done in piston coat.oh yeah dont forget to clearance head for cams and a good valve job.

Exitpupil

The above is the most accurate description on this thread as to how to do your head.

Good luck

Jay

:blush: im honored:evil:

I notice you all seem to worry about taking too much off. Losing velocity is not good yes. If you open the throats at the radius near the valve seat to the size of the valve seat's diameter, you have lost velocity. Also, increasing the port diameter reduces velocity. In theory. But the air speed may increase as a result of increased volume, say on the exhaust side because it flows faster. And your right back where you started from. My motor has alot of torgue and response down low. It has equivelent of .410 cams and 10-1. I'm running an open header with 2.5in. collectors on each side. It has 30yr old coils for spark. I know there's such a thing as too much porting but when for example you install larger valves, the power goes up and I doubt the low end suffers with decent compression. I built a small block chevy with 2.02 valves and switched to 1.94 and man did it lose power. It sounded good but wouldn't pull. Jetting is important here too. I once had 4 straight pipes on my bike and small jets ( they cause restriction and increase velocity through the carb) The motor snapped up quick and back down quick. It sounded good and yes low end torque was good but... naaaa. I drilled out the jets and holy cow. This was without cams. They came out to be 155's. I tried bigger and it sputtered at 6 grand and on. I never did lose any low end. I gained it though. I showed my Dad I could let the clutch out taking off and gas the motor, how the front wheel darn near'd leave the ground. I really wish I had pic's of the how big the ports are, and nice. I bet you'd all laugh, cause it is funny. I think i got close to the oil passages. But it worked for me and I think it would work for all. Now maybe with larger valves you could run into trouble with over porting because after all there is a limit.

Post edited by: nads.com, at: 2006/10/06 00:56

Post edited by: nads.com, at: 2006/10/06 02:44

Nads, I am not afraid of taking too much off the intake side. I can always add it back with JB weld (I have had to do it before). I was just dreaming of a forum filebase documentary on porting since it should be nailed down by now after 25-30 years. I realize that the highest flow numbers are not always the biggest power makers do to cylinder ram filling. Also narrow power bands on the street bite. But, my interest is stirred up. I think I will port this head according to my past experience so I can put the bike on the street. I am going to build a vaccum cleaner home flow bench and do some testing on a junk head for future reference. I'm not racing, but I like knowing I've done the best possible with what I have. The journey is the fun part, otherwise just go buy a new bike. Anyone have a trashed KZ1000 head with at least two good cylinders to donate?

Or you could clean up the casting flash and smooth up the valve bowls on a J model head with some 12.5:1 pistons and have all the flow you would need from the factory, with around 10.5:1 compression

a CSR head would be even better as you could use the tach drive

add those .410 cams and big carbs/good 4/1 header and the front wheel would never stay down

MMMM, I don't have a J head. What do they run?$$

Exitpupil wrote:

MMMM, I don't have a J head. What do they run?$$

i can hook you up with complete bike for $350.00

wireman wrote:

Exitpupil wrote:

MMMM, I don't have a J head. What do they run?$$

i can hook you up with complete bike for $350.00

Not to be nosey Rosey but a whole bike for $350.00:huh: What type of bike is that your talking about?

csr1000,been laid down but motor is unhurt;)